Humble before you start to play with overclocking, do some studying.
OC'd rigs need heavy duty cooling systems. On AMD cpu's you'll need a $80 cooler or even better. I use water cooling, but I'm considering to move to phase-change (compressor) cooling.
Those come in at $600 but then the cpu will go down to -20C

That means some serious overclocking potential. Added bonus is that the system is relatively quiet. OTOH so is watercooling if you do it right.
About the refresh rate fix, do get it ASAP! That flickering 60hz display will give you nothing but a headache.
Rivatuner is a nice utility that not only fixes the refresh rate, but also lets you overclock your geforce untill it screams for mercy.
You should be able to get at least 10% gain in performance with the standard cooling without problems.
Just remember overclocking voids your warranty and is done purely on personal responsibility. Refresh rate fix is safe and a MUST.